Some reviews complain about the assembly, and I imagine this is due to the chair's many parts and many screws. For example, the base of the chair has six parts, not including the wheels: a center piece, and five legs, each leg attached to the center piece with two screws. I've had other (cheaper, weaker) chairs where this is delivered as a single complete piece, or as pieces that slot together without screws. Each arm also has four screws - two attaching the separate pieces of the arm, and then two more to attach it to the seat. The design is also generous with spacers to support the screws - the arms have five spacers each.
However, the single most annoying part of assembling an office is attaching the back to the seat. Generally the attachment is purely with screws, so you have to fully hold two heavy objects close together in an awkward way while you get the screws in. I've done this many times with many chairs and it's always been a massive dreaded pain. This chair's different: the back slides onto a mount attached to the seat, and then, although it still isn't stable without screws, all you have to do is support it while you insert the screws. By reducing the difficulty of the SINGLE worst part of office chair assembly, this chair absolutely doesn't deserve any complaints about its assembly.
For the comfort and ergonomics, I only have one complaint: the arm rotation is adjustable and I have no use for that feature and only ever activate it unintentionally. This chair has a single control for the gas cylinder where a chair five times its price would have three other controls and position locks. Depending on your body type you might not find the dynamic lumbar support comfortable, but for me it's a very nice chair.